Automotive brake systems must satisfy a certain set of consumer expectations such as comfort, durability and reasonable costs. These expectations are translated into a set of specific requirements for the brake system such as a high and stable friction coefficient, vibration and noise characteristics within a predetermined limit, and low wear rates for the friction material and rotor mating services. All of the aforesaid requirements have to be achieved simultaneously at a reasonable cost. Particularly, the performance has to be stable under varying application conditions over extremes in temperature, humidity, speed, and deceleration rate for occasional or many consecutive stops.
Friction materials serve in a variety of ways to control the acceleration and deceleration of vehicles and machines. The friction materials may be resin or rubber bound composites based on asbestos, metallic fibers, or combinations of other organic or inorganic fibers. The friction material is generally composed of binders, reinforcements and fillers.
Brake linings and clutch facings include friction materials which are employed to convert the kinetic energy of the moving vehicle or a machine part into heat to remove the kinetic energy and help the movement of the vehicle or machine part. Typically, the friction material absorbs the heat and gradually dissipates it into the atmosphere. The friction material is considered to be an expendable portion of the disc brake pad, which over a long period of use is converted to wear debris and gases.
Varying formulations of friction materials are frequently employed to enhance predetermined characteristics such as increasing the strength of a friction material, providing varying degrees of wear resistance, heat dissipation, temperature stabilization, and/or high and low temperature friction performance.
Other formulations are also used to provide an abrasive attribute to a friction material. The magnitude of the abrasiveness of the friction material dictates many performance and wear characteristics of the braking system. To that end, extreme abrasiveness will lead to excellent performance but contribute to excessive wear of braking components. Insufficient abrasiveness may protect braking components or provide relatively poor braking characteristics.
It is desirable to maximize the beneficial attributes of some friction material formulations while minimizing the less optimal attributes of the same formulation. It is also desirable to use multiple formulations to maximize the beneficial attributes of the multiple formulations by minimizing the less optimal attributes of the same multiple formulations. It is further desirable to manufacture multiple friction material members with multiple friction material formulations using the same method of manufacture for installation onto the disc pad.